Aerification of turf by turf spiking rather than turf coring, in preparation for selective reseeding or "overseeding", affords several advantages. First, "punching" the turf with spiking tines or spikes rather than coring tines can be used to part the turf and penetrate to soil underlying the turf without leaving small cores of soil and turf lying on the deck. On golf greens, for example, the surface remains available for use without further surface dressing. Second, the spike holes formed in the turf tend to reclose and resume the original surface configuration after reseeding following additional use or rolling of the reseeded area. Finally, seeding of additional plants for turf restoration is accomplished without removing other plants already there.
Successful and satisfactory integration of turf spiking tools and attachments into automated and motor driven turf aerification equipment has, however, not been achieved. The use of turf parting and penetrating spiking tines in turf aerating machines generally results in "divoting" pullup of patches of turf from the underlying soil. As the tines penetrate the turf, the tapered tines tend to "grab" the turf, pulling it out upon retraction of the tines. To avoid this, existing automated and motor driven turf aerators based upon turf punching with spiking tines must use tines arranged at low density with relatively wide spacing between tines in order to avoid turf pullup. As a result there is also low density soil contact seeding, unsatisfactory for high density reseeding and overseeding requirements.
Manual surface preparation tools have been developed to prevent the problem of turf divoting . . . Four United States Patents directed to hand cultivators or "manual tillers" for lawn conditioning were found in a search. The earliest patent reference appears to be the Finkl U.S. Pat. No. 1,965,177 issued in 1934 for a Lawn Cultivating Tool. Finkl discloses the basic concept of a hand tool with "two superimposed plates", a base plate with vertical spikes, and a yieldable plate with apertures aligned with the spikes. The base plate and yieldable plate are held in "parallel spaced relation" by guide rods with coil springs. The plates are mounted at the end of a long handle for manual operation. As explained by Finkl, "during withdrawal of the tool any dirt which might otherwise adhere to the sides of the spikes will be cleared therefrom by the yielding plate . . . ".
Subsequent patents describe variations on this basic turf spiking tool. The Leeper U.S. Pat. No. 3,180,427 adds a locking mechanism for converting the aerating tool to a "tamper" tool. The locking mechanism prevents relative vertical motion of the plates for use in tamping. Leeper also suggests at the end of the specification that "The soil tamping and aerating devices above described may be employed either manually, namely by means of their operating handles . . . , or may be mechanically operated by any suitable reciprocating drive means connected in place of the operating handle." Column 4, Lines 44-48.
The Hochlan U.S. Pat. No. 4,791,995 issued in 1988 describes a similar "manual tiller" and adds the feature of diamond shaped heads on the tines or spikes. In U.S. Pat. No. 3,168,150, Kappler adds the feature of converging or pivotal motion of the tines/fingers in addition to vertical penetration, for correcting depressions or indentations in the golf green. The slight converging motion of the tines upon penetration pushes soil upwardly into a depression to be filled.
Representative patents on the automated turf aerating and cultivating machines include the Collins U.S. Pat. Nos. 4,034,686 and 3,926,131. Collins describes dual tong liquid injector units for injecting liquid treatment material under high pressure into the soil. Six of the injector units are retrofitted on the six vertically reciprocating pistons of a RYAN WG24-1 (Trademark) Turf Aerator. The Collins patents are not directed to turf tools and do not address the problem of turf divoting.
The Eversole U.S. Pat. No. 3,586,109 is directed to a coring "tine" or tool for use on golf green aerators. A comblike element carried by the machine frame is adapted for resting on the ground adjacent the tines and prevents the turf from being lifted when the blocks and the tines move vertically upward. According to this approach for preventing turf pullup or "divoting", the comblike element is connected to the machine frame rather than the tool.
The Kotani U.S. Pat. No. 4,566,543 describes an aerator with a mechanism for controlled depth spiking by a single spike for injecting compressed air into the ground.
The Brown U.S. Pat. No. 3,621,920 describes an automated electric motor lawn aerating machine showing spring loaded shoe stops which bear against the ground during penetration of the low density spiker rod elements Spring bias on the shoe elements helps in removal of the "spiker bits" from the soil. The spring loaded shoe stops however do not form a full ground covering plate parallel with the base plate of the aerating spikes.
Despite the suggestion of Leeper, "manual tillers" of the type described by Finkl but with high density spikes have not been successfully incorporated into automated or motor driven turf aerators of the type described by Collins. The present inventor has discovered that this is the consequence of at least several non-obvious problems encountered in automation of high density turf spiking and in attempts at integration of turf spiking tools into turf aerating machines of the type with motor driven reciprocating pistons. The present invention first recognized these problems and provided nonobvious solutions.